Small molecule CFTR correctors

ABSTRACT

Novel CFTR corrector compounds that are effective in rescuing halide efflux, delF508-CFTR protein processing, and apical functional chloride ion transport in a cell are provided. Also provided are methods for treating protein folding disorders (e.g., cystic fibrosis). The methods include administering a CFTR corrector compound or pharmaceutically acceptable salt or prodrug thereof. Methods of rescuing halide efflux in a cell, correcting a processing defect of a delF508-CFTR protein in a cell, and correcting functional delF508-CFTR chloride channels in a cell are also provided.

CROSS-REFERENCE TO PRIORITY APPLICATION

This application claims priority to U.S. Provisional Application No. 61/728,414, filed Nov. 20, 2012, which is incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY FUNDED RESEARCH

This invention was made with government support under Grant No. NIDDK Phase II SBIR DK084658-03 awarded by the National Institutes of Health. The government has certain rights in the invention.

BACKGROUND

Cystic fibrosis is an example of a protein folding disorder. It is a hereditary disease caused by mutations in a gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). The CFTR gene encodes a chloride channel that is expressed in multiple epithelial cell types. A common CFTR mutation, delF508, causes the failure of CFTR to traffic correctly to the plasma membrane because of protein misfolding. The delF508 mutation is estimated to account for 90% of mutant alleles. Because of its high degree of incidence in the cystic fibrosis population, delF508-CFTR is a prime target for cystic fibrosis therapeutics. As such, delF508-CFTR has been extensively studied and is a model for the study of protein folding diseases.

SUMMARY

Compounds and methods for the treatment of protein folding disorders are provided. Cystic fibrosis (CF) is used throughout as an example of such a protein folding disorder. The methods include administering to a subject a CFTR corrector (i.e., a compound effective in rescuing halide efflux in a cell).

A class of CFTR correctors includes compounds of the following formula:

or pharmaceutically acceptable salts or prodrugs thereof. In this class of compounds, R¹ is substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, or substituted or unsubstituted aryl; R² is hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted aryl; R³ is hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted amino, or substituted carbonyl; and R⁴ is substituted or unsubstituted alkyl, substituted carbonyl, substituted or unsubstituted heteroaryl, or substituted or unsubstituted amino. Optionally, the compound has the following structure:

wherein R⁵, R⁶, R⁷, R⁸, and R⁹ are each independently selected from the group consisting of hydrogen, halogen, hydroxyl, and substituted or unsubstituted alkoxy. Optionally, the compound has the following structure:

Optionally, the compound has the following structure:

wherein R¹⁰ and R¹¹ are each independently selected from the group consisting of hydrogen and substituted or unsubstituted alkyl. Optionally, the compound has the following structure:

wherein R¹² is hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted cycloalkyl. Optionally, the compound is selected from the group consisting of:

A class of CFTR correctors includes compounds of the following structure:

or pharmaceutically acceptable salts or prodrugs thereof. In this class of compounds, R¹, R², and R³ are each independently selected from the group consisting of hydrogen and substituted or unsubstituted alkyl; and R⁴, R⁵, R⁶, R⁷, and R⁸ are each independently selected from the group consisting of hydrogen, halogen, hydroxyl, substituted or unsubstituted alkyl, and substituted or unsubstituted aryl. Optionally, the compound is

A class of CFTR correctors includes compounds of the following formula:

or pharmaceutically acceptable salts or prodrugs thereof. In this class of compounds, X is O or NR¹, wherein R¹ is hydrogen or substituted or unsubstituted alkyl; R² is hydrogen or substituted or unsubstituted alkyl; R³ is hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted cycloalkyl; and R⁴, R⁵, R⁶, R⁷, and R⁸ are each independently selected from the group consisting of hydrogen, halogen, hydroxyl, substituted or unsubstituted alkyl, and substituted or unsubstituted aryl.

Also described herein is a composition comprising one or more of the compounds described herein and a pharmaceutically acceptable carrier.

A method for the treatment of a protein folding disorder in a subject is also described herein. The method for the treatment of a protein folding disorder in a subject comprises administering to the subject an effective amount of a compound as described herein. Optionally, the protein folding disorder is cystic fibrosis.

Also provided herein are methods of rescuing halide efflux in a cell, correcting a processing defect of a delF508-CFTR protein in a cell, and correcting functional delF508-CFTR chloride channels in a cell. The method of rescuing halide efflux in a cell comprises contacting a cell with a compound as described herein, wherein the cell endogenously expresses a CFTR mutation. Optionally, the CFTR mutation is delF508-CFTR. Optionally, the halide efflux is chloride efflux.

A method of correcting a processing defect of a delF508-CFTR protein in a cell comprises contacting a cell with a compound as described herein, wherein the cell expresses a delF508-CFTR mutation. Optionally, the cell is a CF human airway epithelial cell or a CF human lung cell.

A method of correcting functional delF508-CFTR chloride channels in a cell comprises contacting a cell with a compound as described herein, wherein the cell is a polarized epithelial cell. Optionally, the method is performed in vitro. Optionally, the method is performed in vivo.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic showing a general approach for identifying delF508-CFTR correctors.

FIG. 2 is a graph demonstrating the ΔSPQ measurements from SPQ high throughput screening assays for Compounds C-2, C-7, C-9, C-12, and C-16 at increasing dosages.

FIG. 3 is a graph demonstrating the ΔSPQ measurements from SPQ high throughput screening assays for VX-809, DMSO, and Compound C-22.

FIG. 4 is a graph demonstrating the ΔSPQ measurements from SPQ high throughput screening assays for VX-809, DMSO, and Compound C-59.

FIG. 5 is a graph demonstrating the ΔSPQ measurements from SPQ high throughput screening assays for VX-809, DMSO, and Compound C-72.

FIG. 6 is a Western blot demonstrating the delF508 CFTR rescue in CF human airway epithelial cells using Compound C-59 (right panel) and industry standard VX-809 (left panel) at increasing dosages (i.e., 10 nM, 100 nM, 1 μM, and 10 μM). DMSO and low temperature (27° C.) served as the controls.

FIG. 7 is a Western blot demonstrating the delF508 CFTR rescue in CF human airway epithelial cells using Compounds C-2, C-7, C-8, and C-12 at increasing dosages (i.e., 10 nM, 100 nM, 1 μM, and 10 μM). DMSO and low temperature (27° C.) served as the controls.

FIG. 8 is a Western blot demonstrating the delF508 CFTR rescue in CF human airway epithelial cells using Compounds C-2, C-5, C-12, and C-15 at increasing dosages (i.e., 10 nM, 100 nM, 1 μM, and 10 μM). DMSO and low temperature (27° C.) served as the controls.

FIG. 9 is a schematic of an exemplary Ussing chamber-derived short-circuit current trace illustrating the correction of functional apical membrane-resident delF508-CFTR chloride ion channels in a high-resistance CF human airway epithelial cell monolayer with VX-809 (100 nM), DMSO (100 nM) and an existing CFTR corrector (CFCL-2).

FIG. 10 is a schematic of an Ussing chamber-derived short-circuit current trace illustrating the correction of functional apical membrane-resident delF508-CFTR chloride ion channels in a high-resistance CF human airway epithelial cell monolayer with Compound C-15.

FIG. 11 is a schematic of an Ussing chamber-derived short-circuit current trace illustrating the correction of functional apical membrane-resident delF508-CFTR chloride ion channels in a high-resistance CF human airway epithelial cell monolayer with Compound C-73.

FIG. 12 shows the results from the GlyH101-sensitive current analysis in a concentration-response curve plot for Compound C-59.

DETAILED DESCRIPTION

The compounds and methods described herein are useful in the treatment of protein folding disorders. The compounds and methods described herein can be useful, for example, in the treatment of cystic fibrosis, familial hypercholesterolemia, diabetes mellitus, alpha1 antitrypsin deficiency, Fabry's disease, Gaucher's disease, Pompe's disease, hypothyrosis, and Alzheimer's disease. For example, described herein are compounds and methods useful in the treatment of cystic fibrosis. These compounds are able to correct the misfolding or defective trafficking of delF508-CFTR; thus, the compounds are effective as CFTR correctors (i.e., the compounds are effective in rescuing halide efflux in a cell). Methods for screening for CFTR corrector compounds are also described herein.

I. Compounds

A class of CFTR correctors described herein is represented by Formula I:

and pharmaceutically acceptable salts or prodrugs thereof.

In Formula I, R¹ is substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, or substituted or unsubstituted aryl. Optionally, R¹ is substituted phenyl.

Also, in Formula I, R² is hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted aryl. Optionally, R² is hydrogen or methyl.

Additionally, in Formula I, R³ is hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted amino, or substituted carbonyl. Optionally, R³ is hydrogen, methyl, or amino.

Further, in Formula I, R⁴ is substituted or unsubstituted alkyl, substituted carbonyl, substituted or unsubstituted heteroaryl, or substituted or unsubstituted amino. Optionally, R⁴ is an acidic group. Optionally, R⁴ is a carbonyl that can be carboxylic acid or an acid derivative. As used herein, an acid derivative refers to a functional derivative of a carboxylic acid such as, for example, an ester, an amide, acylsulphonamide, or tetrazole. Optionally, R⁴ is —CO₂H or —CO₂CH₂CH₃.

As used herein, the terms alkyl and alkenyl include straight- and branched-chain monovalent substituents. Examples include methyl, ethyl, isobutyl, and the like. Ranges of these groups useful with the compounds and methods described herein include C₁-C₈ alkyl and C₃-C₈ alkenyl.

Heteroalkyl and heteroalkenyl are defined similarly as alkyl and alkenyl, but can contain O, S, or N heteroatoms or combinations thereof within the backbone. Ranges of these groups useful with the compounds and methods described herein include C₁-C₈ heteroalkyl and C₃-C₈ heteroalkenyl.

The terms cycloalkyl and cycloalkenyl include cyclic alkyl groups having a single cyclic ring or multiple condensed rings. Examples include cyclohexyl, cyclopentylethyl, and adamantanyl. Ranges of these groups useful with the compounds and methods described herein include C₃-C₉ cycloalkyl and C₅-C₉ cycloalkenyl.

The terms heterocycloalkyl and heterocycloalkenyl are defined similarly as cycloalkyl and cycloalkenyl, but can contain O, S, or N heteroatoms or combinations thereof within the cyclic backbone. Ranges of these groups useful with the compounds and methods described herein include C₄-C₉ heterocycloalkyl and C₅-C₉ heterocycloalkenyl.

Aryl groups include, for example, phenyl and substituted phenyl. Heteroaryl groups contain O, N, or S heteroatoms, either alone or in combination in five or six membered rings. Examples of heteroaryl groups with one heteroatom include pyridyl, thienyl, and furyl substituted on or joined by any of the available carbon atoms. Examples of heteroaryl groups with more than one heteroatom include pyrimidinyl, oxazolyl, and thiazolyl substituted on or joined by any of the available carbon atoms. Aryl and heteroaryl groups can include additional fused rings. Examples of such groups include indanyl, naphthyl, benzothienyl, quinolinyl, and isomers thereof substituted on or joined by any of the available carbon atoms.

All groups mentioned above can be unsubstituted or substituted with one or more of the following which may the same or different. Examples of appropriate substituents include, but are not limited to, the following: hydroxyl, halogen, haloalkyl (e.g., trifluoromethyl), amino, alkylamino, dialkylamino, alkylsulphonyl, sulphonamides and reverse sulphonamides, amides and reverse amides, alkyl, heteroalkyl, and cycloalkyl.

In some examples of Formula I, when R² is methyl, R³ is methyl, and R⁴ is —CO₂CH₂CH₃, then R¹ is not p-methoxyphenyl, p-fluorophenyl, or p-chlorophenyl. In some examples of Formula I, when R² is methyl, R³ is methyl, and R⁴ is —CO₂CH₃, then R¹ is not p-chlorophenyl.

In some examples, Formula I is represented by Structure I-A:

In Structure I-A, R², R³, and R⁴ are as defined above for Formula I.

Also, in Structure I-A, R⁵, R⁶, R⁷, R⁸, and R⁹ are each independently selected from the group consisting of hydrogen, halogen, hydroxyl, and substituted or unsubstituted alkoxy. Optionally, adjacent R groups in Structure I-A, e.g., R⁵ and R⁶, R⁶ and R⁷, R⁷ and R⁸, or R⁸ and R⁹, can be combined to form a substituted or unsubstituted aryl, substituted or unsubstituted cycloalkenyl, substituted or unsubstituted heteroaryl, or substituted or unsubstituted heterocycloalkenyl. For example, R⁶ and R⁷ can both be methoxy and can combine to form a dioxane.

In some examples, Formula I is represented by Structure I-B:

In Structure I-B, R¹, R², and R³ are as defined above for Formula I. Optionally, the compounds according to Structure I-B can be present as the salt (e.g., an ammonium salt).

In some examples, Formula I is represented by Structure I-C:

In Structure I-C, R¹, R², and R³ are as defined above for Formula I. Also in Structure I-C, R¹⁰ and R¹¹ are each independently selected from the group consisting of hydrogen and substituted or unsubstituted alkyl.

In some examples, Formula I is represented by Structure I-D:

In Structure I-D, R¹, R², and R³ are as defined above for Formula I. Also in Structure I-D, R¹² is selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, and substituted or unsubstituted cycloalkyl.

Examples of Formula I include the following compounds:

A class of CFTR correctors described herein is represented by Formula II:

and pharmaceutically acceptable salts or prodrugs thereof.

In Formula II, R¹, R², and R³ are each independently selected from the group consisting of hydrogen and substituted or unsubstituted alkyl. Optionally, R¹ is methyl. Optionally, R² is hydrogen. Optionally, R³ is methyl.

Also, in Formula II, R⁴, R⁵, R⁶, R⁷, and R⁸ are each independently selected from the group consisting of hydrogen, halogen, hydroxyl, substituted or unsubstituted alkyl, and substituted or unsubstituted aryl.

An example of Formula II includes the following compound:

A class of CFTR correctors described herein is represented by Formula III:

and pharmaceutically acceptable salts or prodrugs thereof.

In Formula III, X is O or NR¹, wherein R¹ is hydrogen or substituted or unsubstituted alkyl.

Also, in Formula III, R² is hydrogen or substituted or unsubstituted alkyl. Optionally, R² is hydrogen.

Additionally, in Formula III, R³ is hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted cycloalkyl.

Further, in Formula III, R⁴, R⁵, R⁶, R⁷, and R⁸ are each independently selected from the group consisting of hydrogen, halogen, hydroxyl, substituted or unsubstituted alkyl, or substituted or unsubstituted aryl. Optionally, R⁵ and R⁶ are chloro. Optionally, R⁴, R⁷, and R⁸ are hydrogen.

Examples of Formula III include the following compounds:

An additional compound useful with the methods described herein includes the following compound:

II. Methods of Making the Compounds

The compounds described herein can be prepared in a variety of ways. The compounds can be synthesized using various synthetic methods. At least some of these methods are known in the art of synthetic organic chemistry. The compounds described herein can be prepared from readily available starting materials. Optimum reaction conditions can vary with the particular reactants or solvent used, but such conditions can be determined by one skilled in the art by routine optimization procedures.

Variations on Formulas I-III and additional compounds described herein include the addition, subtraction, or movement of the various constituents as described for each compound. Similarly, when one or more chiral centers are present in a molecule, all possible chiral variants are included. Additionally, compound synthesis can involve the protection and deprotection of various chemical groups. The use of protection and deprotection, and the selection of appropriate protecting groups can be determined by one skilled in the art. The chemistry of protecting groups can be found, for example, in Greene, et al., Protective Groups in Organic Synthesis, 2d. Ed., Wiley & Sons, 1991, which is incorporated herein by reference in its entirety.

Reactions to produce the compounds described herein can be carried out in solvents, which can be selected by one of skill in the art of organic synthesis. Solvents can be substantially nonreactive with the starting materials (reactants), the intermediates, or products under the conditions at which the reactions are carried out, i.e., temperature and pressure. Reactions can be carried out in one solvent or a mixture of more than one solvent. Product or intermediate formation can be monitored according to any suitable method known in the art. For example, product formation can be monitored by spectroscopic means, such as nuclear magnetic resonance spectroscopy (e.g., ¹H or ¹³C) infrared spectroscopy, spectrophotometry (e.g., UV-visible), or mass spectrometry, or by chromatography such as high performance liquid chromatography (HPLC) or thin layer chromatography.

III. Pharmaceutical Formulations

One or more of the compounds described herein or pharmaceutically acceptable salts or prodrugs thereof can be provided in a pharmaceutical composition comprising a pharmaceutical carrier. Furthermore, the one or more compounds described herein can be combined with other agents, including treatments for lung, digestive, hepatic, and biliary tract related diseases and disorders. For example, in the case of cystic fibrosis, the compounds described herein can be combined with mucus thinning drugs (e.g., dornase alfa, N-Acetyl cysteine, and hypertonic saline), bronchodilators (e.g., metaproterenol sulfate, pirbuterol acetate, salmeterol, albuterol, and terbutaline sulfate), P2Y2-receptor agonists (e.g., denufosol), and agents that target nonsense mutations (e.g., PTC124). Further examples of additional agents that can be combined with the compounds described herein include antibiotics (e.g., aminoglycosides, antipseudomonal penicillins, and cephalosporins), antimicrobial drugs (e.g., rifabutin), ethambutol, clarithromycin, clofazimine, aztreonam, steroidal and nonsteroidal anti-inflammatory drugs (e.g., ibuprofen and prednisone), pentoxifylline, dornase alfa, and ursodeoxycholic acid.

The one or more compounds described herein can be provided as pharmaceutical compositions administered in combination with one or more other therapeutic or prophylactic agents. As used throughout, a therapeutic agent is a compound or composition effective in ameliorating a pathological condition. Illustrative examples of therapeutic agents include, but are not limited to, chemotherapeutic agents, anti-viral agents, anti-opportunistic agents, antibiotics, and immunostimulatory agents. Optionally, more than one therapeutic agent is administered in combination with the provided compositions.

The one or more compounds described herein, with or without additional agents, can be provided in the form of an inhaler or nebulizer for inhalation therapy. As used herein, inhalation therapy refers to the delivery of a therapeutic agent, such as the compounds described herein, in an aerosol form to the respiratory tract (i.e., pulmonary delivery). As used herein, the term aerosol refers to very fine liquid or solid particles carried by a propellant gas under pressure to a site of therapeutic application. When a pharmaceutical aerosol is employed, the aerosol contains the one or more compounds described herein, which can be dissolved, suspended, or emulsified in a mixture of a fluid carrier and a propellant. The aerosol can be in the form of a solution, suspension, emulsion, powder, or semi-solid preparation. Aerosols employed are intended for administration as fine, solid particles or as liquid mists via the respiratory tract of a patient.

The propellant of an aerosol package containing the one or more compounds described herein can be capable of developing pressure within the container to expel the compound when a valve on the aerosol package is opened. Various types of propellants can be utilized, such as fluorinated hydrocarbons (e.g., trichloromonofluromethane, dichlorodifluoromethane, and dichlorotetrafluoroethane) and compressed gases (e.g., nitrogen, carbon dioxide, nitrous oxide, or Freon). The vapor pressure of the aerosol package can be determined by the propellant or propellants that are employed. By varying the proportion of each component propellant, any desired vapor pressure can be obtained within the limits of the vapor pressure of the individual propellants.

As described above, the one or more compounds described herein can be provided with a nebulizer, which is an instrument that generates very fine liquid particles of substantially uniform size in a gas. The liquid containing the one or more compounds described herein can be dispersed as droplets about 5 mm or less in diameter in the form of a mist. The small droplets can be carried by a current of air or oxygen through an outlet tube of the nebulizer. The resulting mist can penetrate into the respiratory tract of the patient.

Additional inhalants useful for delivery of the compounds described herein include intra-oral sprays, mists, metered dose inhalers, and dry powder generators (See Gonda, J. Pharm. Sci. 89:940-945, 2000, which is incorporated herein by reference in its entirety, at least, for inhalation delivery methods taught therein). For example, a powder composition containing the one or more compounds as described herein, with or without a lubricant, carrier, or propellant, can be administered to a patient. The delivery of the one or more compounds in powder form can be carried out with a conventional device for administering a powder pharmaceutical composition by inhalation.

Depending on the intended mode of administration, the pharmaceutical composition can be in the form of solid, semi-solid, or liquid dosage forms, such as, for example, tablets, suppositories, pills, capsules, powders, liquids, aerosols, or suspensions, preferably in unit dosage form suitable for single administration of a precise dosage. The compositions will include a therapeutically effective amount of the compound described herein or derivatives thereof in combination with a pharmaceutically acceptable carrier and, in addition, can include other medicinal agents, pharmaceutical agents, carriers, or diluents. By pharmaceutically acceptable is meant a material that is not biologically or otherwise undesirable, which can be administered to an individual along with the selected compound without causing unacceptable biological effects or interacting in a deleterious manner with the other components of the pharmaceutical composition in which it is contained.

As used herein, the term carrier encompasses any excipient, diluent, filler, salt, buffer, stabilizer, solubilizer, lipid, stabilizer, or other material well known in the art for use in pharmaceutical formulations. The choice of a carrier for use in a composition will depend upon the intended route of administration for the composition. The preparation of pharmaceutically acceptable carriers and formulations containing these materials is described in, e.g., Remington's Pharmaceutical Sciences, 21st Edition, ed. University of the Sciences in Philadelphia, Lippincott, Williams & Wilkins, Philadelphia Pa., 2005. Examples of physiologically acceptable carriers include buffers such as phosphate buffers, citrate buffer, and buffers with other organic acids; antioxidants including ascorbic acid; low molecular weight (less than about 10 residues) polypeptides; proteins, such as serum albumin, gelatin, or immunoglobulins; hydrophilic polymers such as polyvinylpyrrolidone; amino acids such as glycine, glutamine, asparagine, arginine or lysine; monosaccharides, disaccharides, and other carbohydrates including glucose, mannose, or dextrins; chelating agents such as EDTA; sugar alcohols such as mannitol or sorbitol; salt-forming counterions such as sodium; and/or nonionic surfactants such as TWEEN® (ICI, Inc.; Bridgewater, N.J.), polyethylene glycol (PEG), and PLURONICS™ (BASF; Florham Park, N.J.).

Compositions containing the compounds as described herein or pharmaceutically acceptable salts or prodrugs thereof suitable for parenteral injection can comprise physiologically acceptable sterile aqueous or nonaqueous solutions, dispersions, suspensions or emulsions, and sterile powders for reconstitution into sterile injectable solutions or dispersions. Examples of suitable aqueous and nonaqueous carriers, diluents, solvents, or vehicles include water, ethanol, polyols (propyleneglycol, polyethyleneglycol, glycerol, and the like), suitable mixtures thereof, vegetable oils (such as olive oil), and injectable organic esters such as ethyl oleate. Proper fluidity can be maintained, for example, by the use of a coating such as lecithin, by the maintenance of the required particle size in the case of dispersions, and by the use of surfactants.

These compositions can also contain adjuvants such as preserving, wetting, emulsifying, and dispensing agents. Prevention of the action of microorganisms can be promoted by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, and the like. Isotonic agents, for example, sugars, sodium chloride, and the like can also be included. Prolonged absorption of the injectable pharmaceutical form can be brought about by the use of agents delaying absorption, for example, aluminum monostearate and gelatin.

Solid dosage forms for oral administration of the compounds described herein or pharmaceutically acceptable salts or prodrugs thereof include capsules, tablets, pills, powders, and granules. In such solid dosage forms, one or more of the compounds described herein or derivatives thereof is admixed with at least one inert customary excipient (or carrier) such as sodium citrate or dicalcium phosphate or (a) fillers or extenders, as for example, starches, lactose, sucrose, glucose, mannitol, and silicic acid, (b) binders, as for example, carboxymethylcellulose, alignates, gelatin, polyvinylpyrrolidone, sucrose, and acacia, (c) humectants, as for example, glycerol, (d) disintegrating agents, as for example, agar-agar, calcium carbonate, potato or tapioca starch, alginic acid, certain complex silicates, and sodium carbonate, (e) solution retarders, as for example, paraffin, (f) absorption accelerators, as for example, quaternary ammonium compounds, (g) wetting agents, as for example, cetyl alcohol, and glycerol monostearate, (h) adsorbents, as for example, kaolin and bentonite, and (i) lubricants, as for example, talc, calcium stearate, magnesium stearate, solid polyethylene glycols, sodium lauryl sulfate, or mixtures thereof. In the case of capsules, tablets, and pills, the dosage forms can also comprise buffering agents.

Solid compositions of a similar type can also be employed as fillers in soft and hard-filled gelatin capsules using such excipients as lactose or milk sugar as well as high molecular weight polyethyleneglycols, and the like.

Solid dosage forms such as tablets, dragees, capsules, pills, and granules can be prepared with coatings and shells, such as enteric coatings and others known in the art. They can contain opacifying agents and can also be of such composition that they release the active compound or compounds in a certain part of the intestinal tract in a delayed manner. Examples of embedding compositions that can be used are polymeric substances and waxes. The active compounds can also be in micro-encapsulated form, if appropriate, with one or more of the above-mentioned excipients.

Liquid dosage forms for oral administration of the compounds described herein or pharmaceutically acceptable salts or prodrugs thereof include pharmaceutically acceptable emulsions, solutions, suspensions, syrups, and elixirs. In addition to the active compounds, the liquid dosage forms can contain inert diluents commonly used in the art, such as water or other solvents, solubilizing agents, and emulsifiers, as for example, ethyl alcohol, isopropyl alcohol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl benzoate, propyleneglycol, 1,3-butyleneglycol, dimethylformamide, oils, in particular, cottonseed oil, groundnut oil, corn germ oil, olive oil, castor oil, sesame oil, glycerol, tetrahydrofurfuryl alcohol, polyethyleneglycols, and fatty acid esters of sorbitan, or mixtures of these substances, and the like.

Besides such inert diluents, the composition can also include additional agents, such as wetting, emulsifying, suspending, sweetening, flavoring, or perfuming agents.

Suspensions, in addition to the active compounds, can contain additional agents, as for example, ethoxylated isostearyl alcohols, polyoxyethylene sorbitol and sorbitan esters, microcrystalline cellulose, aluminum metahydroxide, bentonite, agar-agar and tragacanth, or mixtures of these substances, and the like.

Compositions of the compounds described herein or pharmaceutically acceptable salts or prodrugs thereof for rectal administration are optionally suppositories, which can be prepared by mixing the compounds with suitable non-irritating excipients or carriers such as cocoa butter, polyethyleneglycol or a suppository wax, which are solid at ordinary temperatures but liquid at body temperature and therefore, melt in the rectum or vaginal cavity and release the active component.

Dosage forms for topical administration of the compounds described herein or pharmaceutically acceptable salts or prodrugs thereof include ointments, powders, sprays, aerosols, and inhalants (e.g., intra-oral sprays, mists, metered dose inhalers, nebulizers, and dry powder generators). The compounds described herein or pharmaceutically salts or prodrugs thereof are admixed under sterile conditions with a physiologically acceptable carrier and any preservatives, buffers, or propellants as can be required. Ophthalmic formulations, ointments, powders, and solutions are also contemplated as being within the scope of the compositions.

The term pharmaceutically acceptable salts as used herein refers to those salts of the compound described herein or derivatives thereof that are, within the scope of sound medical judgment, suitable for use in contact with the tissues of subjects without undue toxicity, irritation, allergic response, and the like, commensurate with a reasonable benefit/risk ratio, and effective for their intended use, as well as the zwitterionic forms, where possible, of the compounds described herein. The term salts refers to the relatively non-toxic, inorganic and organic acid addition salts of the compounds described herein. These salts can be prepared in situ during the isolation and purification of the compounds or by separately reacting the purified compound in its free base form with a suitable organic or inorganic acid and isolating the salt thus formed. Representative salts include the hydrobromide, hydrochloride, sulfate, bisulfate, nitrate, acetate, oxalate, valerate, oleate, palmitate, stearate, laurate, borate, benzoate, lactate, phosphate, tosylate, citrate, maleate, fumarate, succinate, tartrate, naphthylate mesylate, glucoheptonate, lactobionate, methane sulphonate, and laurylsulphonate salts, and the like. These can include cations based on the alkali and alkaline earth metals, such as sodium, lithium, potassium, calcium, magnesium, and the like, as well as non-toxic ammonium, quaternary ammonium, and amine cations including, but not limited to ammonium, tetramethylammonium, tetraethylammonium, methylamine, dimethylamine, trimethylamine, triethylamine, ethylamine, and the like. (See Stahl and Wermuth, Pharmaceutical Salts: Properties, Selection, and Use, Wiley-VCH, 2008, which is incorporated herein by reference in its entirety, at least, for compositions taught therein.)

Administration of compounds described herein or pharmaceutically acceptable salts or prodrugs thereof can be carried out using therapeutically effective amounts of the compounds described herein or pharmaceutically acceptable salts or prodrugs thereof for periods of time effective to treat neurological disorders. The effective amount of the compounds described herein or pharmaceutically acceptable salts or prodrugs thereof can be determined by one of ordinary skill in the art and includes exemplary dosage amounts for a mammal of from about 0.5 to about 200 mg/kg of body weight of active compound per day, which can be administered in a single dose or in the form of individual divided doses, such as from 1 to 4 times per day. Alternatively, the dosage amount can be from about 0.5 to about 150 mg/kg of body weight of active compound per day, about 0.5 to 100 mg/kg of body weight of active compound per day, about 0.5 to about 75 mg/kg of body weight of active compound per day, about 0.5 to about 50 mg/kg of body weight of active compound per day, about 0.5 to about 25 mg/kg of body weight of active compound per day, about 1 to about 20 mg/kg of body weight of active compound per day, about 1 to about 10 mg/kg of body weight of active compound per day, about 20 mg/kg of body weight of active compound per day, about 10 mg/kg of body weight of active compound per day, or about 5 mg/kg of body weight of active compound per day. Those of skill in the art will understand that the specific dose level and frequency of dosage for any particular subject can be varied and will depend upon a variety of factors, including the activity of the specific compound employed, the metabolic stability and length of action of that compound, the species, age, body weight, general health, sex and diet of the subject, the mode and time of administration, rate of excretion, drug combination, and severity of the particular condition.

IV. Methods of Use

The methods described herein include a method of treating protein folding disorders (e.g., cystic fibrosis) in a subject. These methods include the step of administering to the subject a compound of the structures described herein. Additional steps can be included in the method described herein. For example, the methods can further include the steps of selecting a subject with a protein folding disorder, such as cystic fibrosis, and administering to the subject one or more of the CFTR correctors described herein.

In the methods described herein, the subjects treated can be further treated with one or more additional agents. The one or more additional agents and the compounds described herein or pharmaceutically acceptable salts or prodrugs thereof can be administered together in a single composition (e.g., as an admixture) or in separate compositions in any order, including simultaneous administration, as well as temporally spaced order of up to several days apart. The methods can also include more than a single administration of the one or more additional agents and/or the compounds described herein or pharmaceutically acceptable salts or prodrugs thereof. The administration of the one or more additional agents and the compounds described herein or pharmaceutically acceptable salts or prodrugs thereof can be by the same or different routes and concurrently or sequentially.

As described above, the compounds described herein are useful in the treatment of protein folding disorders. Examples of protein folding disorders include cystic fibrosis; neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, Creutzfeld-Jakob disease, Kuru, GSS disease, Huntington's disease, Polyglutamine diseases, Prion disease, Bovine Spongiform Encephalopathy (BSE), Amyotrophic Lateral Sclerosis, Alexander's disease, Primary Systemic Amyloidosis, Secondary Systemic Amyloidosis, Senile Systemic Amyloidosis, and Amyloidosis in senescence; ocular diseases such as Cataract, Retinitis Pigmentosa, and Macular Degeneration; and other diseases such as Islet amyloid, Medullar Carcinoma of the Thyroid, Hereditary Renal Amyloidosis, Hemodialysis-related amyloidosis, Desmin-related Cardiomyopathy, Charcot-Marie Tooth disease, diabetes insipidis, alpha1 antitrypsin deficiency, Fabry's disease, Gaucher's disease, and Pompe's disease. The compounds described herein are also useful in the treatment of chronic obstructive pulmonary diseases (COPD), including chronic bronchitis and/or emphysema (e.g., emphysema caused by smoking or by exposure to smoke). CFTR mRNA and protein are down-regulated in the COPD umbrella of diseases.

The compounds described herein are also useful in rescuing halide efflux in a cell, correcting the protein processing defect in a cell, and correcting functional delF508-CFTR chloride channels in a cell. The methods of rescuing halide efflux in a cell include contacting a cell with a compound as described herein. In these methods, the cell endogenously expresses a CFTR mutation. Optionally, the CFTR mutation is delF508-CFTR. Optionally, the halide efflux is chloride efflux.

The methods of correcting a processing defect of a delF508-CFTR protein in a cell include contacting a cell with a compound as described herein. In these methods, the cell expresses a delF508-CFTR mutation. Optionally, the cell is a CF human airway epithelial cell or a CF human lung.

The methods of correcting functional delF508-CFTR chloride channels in a cell include contacting a cell with a compound as described herein. Optionally, the chloride channels are in the apical membrane of a polarized epithelial cell. Optionally, the method is performed in vitro or in vivo.

V. Methods of Profiling

Additionally, a method of profiling a compound for treating cystic fibrosis (i.e., a CFTR corrector) is provided. The methods employ assays that can gauge the relative potency and efficacy of the compounds described herein, as compared to a control, for treating a protein folding disorder such as cystic fibrosis. The methods optionally include a CF bronchial epithelial cell that endogenously expresses a CFTR mutation (e.g., the delF508-CFTR mutation). The cell can be, for example, a primary or immortal CF lung and/or airway epithelial cell (e.g., CFBE41o− cells). CFBE41o− cells are human airway epithelial cells on a delF508-CFTR homozygous background. Optionally, the cells do not overexpress the CFTR mutation.

The cell models used in other methods of identifying CFTR correctors have employed low temperature, chemical chaperones such as glycerol, 4-phenylbutyrate, DMSO, and overexpression of CFTR in a transduced Fisher rat thyroid cell line as the model. The present methods do not require, and optionally exclude, over-expression of CFTR, low temperature, and chemical chaperones, which are variables that can distort the results.

The method of profiling can include detecting the rescue of halide efflux from a cell. The step of detecting a rescue of halide efflux from the cell can be monitored using the halide quenched dye 6-methoxy-N-(3-sulfopropyl)-quinolinium (SPQ, Molecular Probes Inc., Eugene, Oreg.). In this method, cells are treated with a compound as described herein for a period of time (e.g., 48 hours). The rescue or correction of halide efflux is then detected using the SPQ assay with the halide dye. The degree of halide efflux rescue or correction indicates that the compound has corrected delF508-CFTR-driven membrane chloride ion transport and is, therefore, useful in treating cystic fibrosis. Optionally, the halide efflux is chloride efflux. The method of screening can further comprise performing the method with multiple concentrations of the compound.

The method of profiling can also include determining the degree of CFTR glycosylation or CFTR protein processing. Optionally, this method can be performed using Western blot analysis. In this method, cells can be treated with the compound as described herein for a period of time (e.g., 24 hours) and, optionally, at multiple concentrations (e.g., 4 doses).

The method of profiling can further include determining the degree of functional delF508-CFTR chloride ion channels in the apical cell membrane of cells (e.g., polarized CF human airway epithelial cells). This method can use electrophysiological methods, such as Ussing chamber-based measurement of short-circuit current, voltammeter-based measurement of open-circuit transepithelial voltage and transepithelial resistance, and patch-clamp electrophysiology.

In general, compounds useful for treating cystic fibrosis can be identified from large libraries of natural products or synthetic (or semi-synthetic) extracts or chemical libraries according to methods known in the art. The precise source of test extracts or compounds is not critical to the screening procedure(s). Accordingly, virtually any number of chemical extracts or compounds can be screened using the methods described herein. Examples of such extracts or compounds include, but are not limited to, plant-, fungal-, prokaryotic- or animal-based extracts, fermentation broths, and synthetic compounds, as well as modifications of existing compounds. Numerous methods are also available for generating random or directed synthesis (e.g., semi-synthesis or total synthesis) of any number of chemical compounds, including, but not limited to, saccharide-, lipid-, peptide-, polypeptide- and nucleic acid-based compounds. Synthetic compound libraries and libraries of natural compounds in the form of bacterial, fungal, plant, and animal extracts are commercially available. In addition, natural and synthetically produced libraries are generated, if desired, according to methods known in the art, e.g., by standard extraction and fractionation methods. Furthermore, if desired, any library or compound is readily modified using standard chemical, physical, or biochemical methods.

As used herein, the terms treatment, treating, or treat refer to a method of reducing or delaying the onset of one or more signs or symptoms or an improvement in the clinical state of the subject being treated for a disease or disorder (e.g., cystic fibrosis). Thus, in the disclosed method, treatment can refer to a 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100% reduction in the severity of one or more symptoms of a disease or condition. For example, reduced numbers of infections or hospitalizations, reduction in respiratory or gastrointestinal symptoms, improved nutritional status, or improved pulmonary function in the subject as compared to a control indicate effective treatment. As used herein, control refers to the untreated condition (e.g., the subject not treated with the compounds and compositions described herein). Thus, the reduction can be a 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%, or any percent reduction in between 10% and 100% as compared to native or control levels. It is understood that treatment does not necessarily refer to a cure or complete ablation of the disease, condition, or symptoms of the disease or condition.

As used herein, the terms prevent, preventing, and prevention of a disease or disorder refer to an action, for example, administration of a composition or therapeutic agent, that occurs before or at about the same time a subject begins to show one or more symptoms of the disease or disorder, which inhibits or delays onset or severity of one or more symptoms of the disease or disorder.

As used herein, references to decreasing, reducing, or inhibiting include a change of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or greater as compared to a control level. Such terms can include, but do not necessarily include, complete elimination.

As used herein, subject means both mammals and non-mammals. Mammals include, for example, humans; non-human primates, e.g., apes and monkeys; cattle; horses; sheep; rats; mice; pigs; and goats. Non-mammals include, for example, fish and birds.

Throughout this application, various publications are referenced. The disclosures of these publications in their entireties are hereby incorporated by reference into this application.

The examples below are intended to further illustrate certain aspects of the methods and compounds described herein, and are not intended to limit the scope of the claims.

EXAMPLES Example 1: Synthesis

A synthetic scheme for 4-(3,4-dichlorophenyl)-3-methyl-1H-pyrazol-5-amine, a precursor used to prepare the compounds described herein, is provided in Scheme 1.

A synthetic scheme for Compounds C-5 and C-15 is shown in Scheme 2.

A synthetic scheme for Compounds C-12 and C-2 is shown in Scheme 3.

A synthetic scheme for Compound C-22 is shown in Scheme 4.

A synthetic scheme for Compound C-25 is shown in Scheme 5.

A synthetic scheme for Compound C-59 is shown in Scheme 6.

Example 2: Compound Profiling

A schematic showing a general approach for profiling the CFTR corrector drugs described herein is shown in FIG. 1. The compounds were initially subjected to the SPQ halide-sensitive fluorescence dye profiling assay for rescue or correction of membrane chloride ion permeability or transport with an 8-point concentration-response curve. The EC₅₀ values for the compounds described herein were determined and compared to the efficacy of the industry standard Vertex 809 (VX-809; Vertex Pharmaceuticals, Cambridge, Mass.) at 3 μM, which is the maximally effective profiling dose for VX-809 (Table 1). The VX-809 dosage at 3 μM was treated as having 100% efficacy in the comparison. Those compounds that showed superior potency and efficacy to VX-809 (i.e., Compounds C-2, C-5, C-12, C-15, C-22, C-25, C-55, C-59, and C-73) were subjected to both Ussing chamber electrophysiology and biochemical correction bioassays for further profiling.

TABLE 1 Efficacy Comparison Compound ID EC₅₀ (μM) % Efficacy to 3 μM VX-809 C-1 1.9 200 — C-2 1.0 170 10-fold greater than VX-809 C-3 11.5 200 Equivalent to VX-809 C-4 No effect 0 N/A C-5 0.1 160 10-fold greater than VX-809 C-6 9.9 170 3-fold greater than VX-809 C-7 7 220 3-fold greater than VX-809 C-8 5.7 155 2-fold greater than VX-809 C-9 17.8 120 Less than VX-809 C-10 No effect 40 N/A C-11 No effect 0 N/A C-12 1.0 120 7-fold greater than VX-809 C-13 No effect (toxic) 0 N/A C-14 No effect 0 N/A C-15 0.3 120 10-fold greater than VX-809 C-16 2.2 80 2-fold greater than VX-809 C-17 >30 75 Equivalent to VX-809 C-18 3.1 20 Less than VX-809 C-19 No effect 0 N/A C-20 2.0 100 2.5-fold greater than VX-809 C-21 1.1 50 2.5-fold greater than VX-809 C-22 1.3 130 12-fold greater than VX-809 C-23 Not determined 110 Equivalent to VX-809 (no plateau) C-24 14.2 140 Equivalent to VX-809 C-25 0.83 100 10-fold greater than VX-809 C-26.1 No effect (toxic 0 N/A at 10 μM and above) C-26.2 No effect (toxic 0 N/A at 10 μM and above) C-27 3.3 90 2-fold greater than VX-809 C-28.1 No effect 0 N/A C-29 No effect 0 N/A C-30 26.3 50 Less than VX-809 C-31 No effect 0 N/A C-32 6 160 2.5-fold greater than VX-809 C-32.1 No effect (toxic 5 N/A at 10 μM and above) C-34 0.58 (may be 0 N/A toxic at 10 μM and above) C-35 0.7 100 Equivalent to VX-809 C-36 4.8 50 Equivalent to VX-809 C-37 5.1 80 Equivalent to VX-809 C-40 No effect (toxic 0 N/A at 10 μM and above) C-41 No effect 0 N/A C-42 No effect 5 N/A C-43 11 50 Equivalent to VX-809 C-45 2.5 50 Equivalent to VX-809 C-49 2 50 Equivalent to VX-809 C-50 0.5 30 Equivalent to VX-809 C-51 3.4 50 Equivalent to VX-809 C-52 20 70 Less than VX-809 C-53 Not determined 75 Less than VX-809 (no plateau) C-54 6.7 125 2-fold greater than VX-809 C-55 0.66 100 10-fold greater than VX-809 C-56 11.6 20 Less than VX-809 C-57 12.0 20 N/A C-58 Not determined 100 N/A C-59 0.16 110 15-fold greater than VX-809 C-59.1 10.5 40 Less than VX-809 C-60 No effect 0 N/A C-66 Not determined 25 N/A C-66.1 No effect 0 N/A C-66.2 11 100 — C-68 Not determined 25 N/A C-68.1 Not determined 20 N/A C-70 3.7 110 2-fold greater than VX-809 C-71 6.9 130 Equivalent to VX-809 C-71.1 Not determined 0 N/A (toxic) C-72 2.3 90 — C-72.1 — — — C-73 1.1 125 5-fold greater than VX-809 C-73.1 Not determined −75 N/A (toxic) C-74 — — —

Example 3: SPQ High Throughput Screening Assay

To perform the SPQ high throughput screening assay, CFBE41o− cells were seeded into 96-well microtiter plates and were loaded with the fluorescent halide-sensitive dye, SPQ, in serum-containing culture medium. Certain wells were loaded with known positive control corrector molecules, including VX-809. The test compounds were loaded into wells and were tested in triplicate wells at a 10 μM dose and incubated over 48 hours at room temperature. During the 48 hour period, SPQ was absorbed. Plates were washed in a sodium chloride (NaCl) based Ringer and read once over two minutes to set the baseline SPQ fluorescence activity. Then, NaCl was replaced by sodium nitrate (NaNO₃) based Ringer. The plates were read twice over four minutes. The primary high throughput screen (HTS) data were analyzed to detect any function of rescued delF508-CFTR under basal conditions. The plate was read up to two times to complete the SPQ HTS assay.

Example 4: CFTR Western Blot

The method described in Example 3 was repeated with doses of the test compound of 0.01 μM, 0.1 μM, 1 μM, 10 μM, and 50 μM in Dulbecco's Modified Eagle Medium (DMEM) with 10% fetal bovine serum (FBS) for 48 hours at 37° C. Unaltered CFBE41o− cells were used as the model. A Western blot analysis of the lysates (10-50 μg total protein) was performed using the MM13-4 antibody for human CFTR to monitor changes in the CFTR protein. The most effective concentrations and time courses (12-96 h) were determined. By way of example, graphs showing the dose response results for exemplary compounds are provided in FIGS. 2-5. VX-809 and DMSO were used as the controls.

CFTR was immunoprecipitated under mild detergent conditions (1% digitonin, 2.5 mM HEPES, 10.0 mM CaCl₂, pH 7.6). The isolated protein complexes were run on SDS-PAGE gels and analyzed by mass spectroscopy. The CFBE41o− control cells were lysed in 2% digitonin (2.5 mM HEPES, 10.0 mM CaCl₂, pH 7.6). All lysis buffers were supplemented with a protease inhibitor cocktail (Complete Mini, Roche, Nutley, N.J.). CFTR was immunoprecipitated using Protein A-immobilized agarose beads and antibodies to the C-terminus of CFTR or to the second nucleotide-binding domain. The antibodies were covalently coupled to agarose beads before use (PROFOUND Mammalian Co-IP Kit, Pierce, Rockford, Ill.). The immunoprecipitated CFTR complexes were run on gels, and the interacting proteins were analyzed by mass spectroscopy.

Cells were lysed in RIPA buffer (50 mM Tris-HCl, pH 7.4, 150 mM NaCl, 1% NP-40, 0.5% Deoxycholic Acid, 0.1% SDS) plus a cocktail of protease inhibitors (Roche; Basel, Switzerland). Protein concentrations in the cell lysates were measured by BCA Protein Assay using BSA as standard (Pierce; Rockford, Ill.). Proteins (25 μg) were resolved on an 8% SDS-PAGE gel and transferred to PDVF membranes. Total CFTR in the lysate was detected by immunoblotting using a specific CFTR antibody (MM13-4 from Upstate, 1:500 dilution).

The compounds were then subjected to a biochemical assay to define which hit compounds rescued the band B core glycosylated endoplasmic reticulum (ER) form of delF508-CFTR within the cell interior into the maturely glycosylated band C form within the secretory pathway for proteins and within the plasma membrane. Effective compounds stabilized the band B form of CFTR and caused more of this form to accumulate at the level of the ER. The most effective compounds caused the band C form to appear.

By way of example, the delF508-CFTR mutation can be rescued from the ER with low temperature incubation for 48 hours (see examples in the blots as the positive control). The DMSO control is the simulated CF condition where the delF508-CFTR-expressing cells were grown at physiological temperature.

Certain compounds described herein were also tested in the biochemical rescue assay. Each compound was tested at 10 μM, 1 μM, 10 nM, and 100 nM. DMSO, VX-809 treated cells, WT-CFTR expressing cells, and low temperature (27° C.) corrected cells served as the controls. See FIGS. 6-8. The experiments were performed in 10% serum containing medium using the method as described above. The data demonstrate that the corrector compounds described herein are effective independent of serum protein. Specifically, Compounds C-2, C-12, and C-15 showed biochemical correction of the delF508-CFTR protein in CF human airway epithelial cells.

Example 5: Electrical Measurements

An electrical assay was also performed to determine the functional rescue of delF508-CFTR to the apical cell membrane in a polarized epithelium using the compounds described herein. The metrics analyzed were the basal short-circuit Cl⁻ current, the change or delta Cl⁻ current stimulated by forskolin, the total stimulated Cl⁻ current (basal and forskolin), and the change or delta Cl⁻ current inhibited by GlyH101. For exemplary purposes, DMSO (100 nM) and VX-809 (100 nM equivalent) treatments were controls, and a CFCL corrector was tested (see FIG. 9).

Only high-resistance cell monolayers (>800 to 1,000 Ohms per cm²) were used in the experiments. Basal short-circuit current (I_(SC)) was measured and documented. Amiloride was added to the apical side of the Ussing chamber to block any contribution of ENaC or other sodium or cation channels under basal or stimulated conditions. The effect of amiloride was negligible under these cell culture conditions. In the continued presence of amiloride (100 μM), forskolin (10 μM) was added to both sides of the monolayer to selectively open any delF508-CFTR chloride channels in the apical cell membrane. This activation step uncovered any remaining corrected delF508-CFTR chloride ion channels in the apical membrane of the polarized CF human bronchial epithelium. The final step was the addition of a CFTR-selective inhibitor, GlyH101 (100 μM), to reverse the effect of forskolin. The inhibitor also blocked some of the basally active current, validating that it is CFTR-driven current.

Ussing chamber-derived short-circuit current data were obtained for Compounds C-15 and C-73 (see FIGS. 10 and 11). Compound C-15 shows robust correction of functional delF508-CFTR chloride ion channels in the apical membrane of a polarized CF human bronchial epithelium (see FIG. 10). Furthermore, FIG. 10 demonstrates that the Vertex CFTR potentiator compound, VX-770 (Kalydeco), opens some additional delF508-CFTR channels in the presence of forskolin. This indicates that the currents are carried by CFTR channels. Compound C-73 showed superior potency and equivalent to greater efficacy versus VX-809. The same protocol of additions of drugs to the apical side of the Ussing chamber was performed on each cell monolayer as described above. Final concentrations of drugs are shown in FIG. 11. CPT-cAMP and IBMX are equivalent and CFTR-specific agonists to forskolin. As described above, VX-770 is a CFTR potentiator drug added to activate any remaining corrected CFTR present. The concentration-response curve plot for Compound C-59 shows that increasing concentrations of Compound C-59 (x-axis) stimulate increased amounts of GlyH101-sensitive current (see FIG. 12).

The compounds and methods of the appended claims are not limited in scope by the specific compounds and methods described herein, which are intended as illustrations of a few aspects of the claims and any compounds and methods that are functionally equivalent are within the scope of this disclosure. Various modifications of the compounds and methods in addition to those shown and described herein are intended to fall within the scope of the appended claims. Further, while only certain representative compounds, methods, and aspects of these compounds and methods are specifically described, other compounds and methods are intended to fall within the scope of the appended claims. Thus, a combination of steps, elements, components, or constituents can be explicitly mentioned herein; however, all other combinations of steps, elements, components, and constituents are included, even though not explicitly stated. 

What is claimed is:
 1. A compound of the following formula:

or a pharmaceutically acceptable salt thereof, wherein: R¹ is substituted aryl; R² is hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted aryl; and R³ is hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted amino, or substituted carbonyl, wherein when R² is hydrogen and R³ is methyl, then R¹ is not p-chlorophenyl.
 2. A compound of the following formula:

or a pharmaceutically acceptable salt thereof, wherein R¹ is substituted aryl; R² is hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted aryl; R³ is hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted amino, or substituted carbonyl; and R¹⁰ and R¹¹ are each independently selected from the group consisting of hydrogen and substituted or unsubstituted alkyl.
 3. A compound of the following formula:

or a pharmaceutically acceptable salt thereof, wherein R¹ is substituted aryl; R² is hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted aryl; R³ is hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted amino, or substituted carbonyl; and R¹² is hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted cycloalkyl, wherein when R² is hydrogen and R³ is methyl, then R¹ is not p-chlorophenyl.
 4. A compound selected from the group consisting of:


5. A compound of the following formula:

or a pharmaceutically acceptable salt thereof, wherein: R¹, R², and R³ are each independently selected from the group consisting of hydrogen and substituted or unsubstituted alkyl; and R⁴, R⁵, R⁶, R⁷, and R⁸ are each independently selected from the group consisting of hydrogen, halogen, hydroxyl, substituted or unsubstituted alkyl, and substituted or unsubstituted aryl.
 6. The compound of claim 5, wherein the compound is


7. A compound of the following formula:

or a pharmaceutically acceptable salt thereof, wherein: X is O or NR¹, wherein R¹ is hydrogen or substituted or unsubstituted alkyl; R² is hydrogen; R³ is hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted cycloalkyl; and R⁴, R⁵, R⁶, R⁷, and R⁸ are each independently selected from the group consisting of hydrogen, halogen, hydroxyl, substituted or unsubstituted alkyl, and substituted or unsubstituted aryl.
 8. A composition comprising the compound of claim 1 and a pharmaceutically acceptable carrier.
 9. A method for the treatment of a protein folding disorder in a subject, comprising: administering to the subject an effective amount of a compound of claim
 1. 10. The method of claim 9, wherein the protein folding disorder is cystic fibrosis.
 11. A method of rescuing halide efflux in a cell, comprising: contacting a cell with a compound of claim 1, wherein the cell endogenously expresses a CFTR mutation.
 12. The method of claim 11, wherein the CFTR mutation is delF508-CFTR.
 13. The method of claim 11, wherein the halide efflux is chloride efflux.
 14. A method of correcting a processing defect of a delF508-CFTR protein in a cell, comprising: contacting a cell with a compound of claim 1, wherein the cell expresses a delF508-CFTR mutation.
 15. The method of claim 11, wherein the cell is a CF human airway epithelial cell.
 16. The method of claim 11, wherein the cell is a CF human lung.
 17. A method of correcting functional delF508-CFTR chloride channels in a cell, comprising: contacting a cell with a compound of claim 1, wherein the cell is a polarized epithelial cell.
 18. The method of claim 11, wherein the method is performed in vitro.
 19. The method of claim 11, wherein the method is performed in vivo.
 20. The compound of claim 1, wherein the compound has the following structure: 